WASHINGTON (Reuters) - Arkema SA expects chemicals to catch fire or explode at its heavily flooded plant in Crosby, Texas in the coming days, and has no way to prevent that from happening, the chief executive officer of the company's North America unit said on Wednesday.

The company evacuated remaining workers on Tuesday and Harris County ordered the evacuation of residents in a 1.5-mile(2.4-km) radius of the plant that makes organic chemicals.

Richard Rowe, chief executive officer of the North America unit, told reporters that chemicals on the site will catch fire and explode if they are not properly cooled, and that Arkema expects that to happen within the next six days as temperatures rise. He said the company has no way to prevent that because the plant is swamped by about six feet (1.83 m) of water.

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HOUSTON, TX - AUGUST 28: Barb Davis, 74. is helped to dry land after being rescued from her flooded neighborhood after it was inundated with rain water, remnants of Hurricane Harvey, on August 28, 2017 in Houston, Texas. Harvey, which made landfall north of Corpus Christi late Friday evening, is expected to dump upwards to 40 inches of rain in areas of Texas over the next couple of days. (Photo by Scott Olson/Getty Images)

HOUSTON, TX - AUGUST 28: People are rescued from a flooded neighborhood after it was inundated with rain water, remnants of Hurricane Harvey, on August 28, 2017 in Houston, Texas. Harvey, which made landfall north of Corpus Christi late Friday evening, is expected to dump upwards to 40 inches of rain in areas of Texas over the next couple of days. (Photo by Scott Olson/Getty Images)

HOUSTON, TX - AUGUST 28: People are rescued from a flooded neighborhood after it was inundated with rain water, remnants of Hurricane Harvey, on August 28, 2017 in Houston, Texas. Harvey, which made landfall north of Corpus Christi late Friday evening, is expected to dump upwards to 40 inches of rain in areas of Texas over the next couple of days. (Photo by Scott Olson/Getty Images)

HOUSTON, TX - AUGUST 28: People are rescued from a flooded neighborhood after it was inundated with rain water, remnants of Hurricane Harvey, on August 28, 2017 in Houston, Texas. Harvey, which made landfall north of Corpus Christi late Friday evening, is expected to dump upwards to 40 inches of rain in areas of Texas over the next couple of days. (Photo by Scott Olson/Getty Images)

A boy and girl hug their grandmothers' dogs after being rescued from rising floodwaters due to Hurricane Harvey in Spring, Texas, U.S., on Monday, Aug. 28, 2017. A deluge of rain and rising floodwaters leftï¿½Houstonï¿½immersed and helpless,ï¿½crippling a global center of the oil industry and testing the economic resiliency of a state that's home to almost 1 in 12 U.S. workers. Photographer: Luke Sharrett/Bloomberg via Getty Images

Rescuers help a woman from a flooded retirement home into a boat after Hurricane Harvey in Spring, Texas, U.S., on Monday, Aug. 28, 2017. A deluge of rain and rising floodwaters leftï¿½Houstonï¿½immersed and helpless,ï¿½crippling a global center of the oil industry and testing the economic resiliency of a state that's home to almost 1 in 12 U.S. workers. Photographer: Luke Sharrett/Bloomberg via Getty Images

HOUSTON, TX - AUGUST 28: People wait for a ride to a shelter after being rescued from a flooded neighborhood when it was inundated with rain water, remnants of Hurricane Harvey, on August 28, 2017 in Houston, Texas. Harvey, which made landfall north of Corpus Christi late Friday evening, is expected to dump upwards to 40 inches of rain in areas of Texas over the next couple of days. (Photo by Scott Olson/Getty Images)

HOUSTON, TX - AUGUST 28: Dean Mize holds children as he and Jason Legnon use an airboat to rescue people from homes that are inundated with flooding from Hurricane Harvey on August 28, 2017 in Houston, Texas. Harvey, which made landfall north of Corpus Christi late Friday evening, is expected to dump upwards to 40 inches of rain in Texas over the next couple of days. (Photo by Joe Raedle/Getty Images)

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Rowe said the company was "comfortable" with the size of the evacuation zone.

Rowe did not disclose the volume of chemicals on the site and said it was speculative to predict how much damage the plant could sustain. He said there could be an "intense fire" that would result in significant black smoke but would not pose any "long-term harm or impact."

The plant is near a section of Interstate-90 that has been underwater and closed.

The plant has been without electric service since Sunday. Back-up generators have largely been inundated with water, the company said.

Chemicals on site are stored at low temperatures and can catch fire or explode at higher temperatures. The plant lost refrigeration when backup generators were flooded and then workers transferred products from the warehouses into diesel-powered refrigerated containers. The company said some refrigeration of back-up containers has been compromised because of high-water levels and the company is monitoring temperature levels remotely.

The Federal Aviation Administration has temporarily barred flights over the area near the plant because of the risk of fire or explosion.

Harvey, which came ashore in Texas last week as a powerful Category 4 hurricane, has caused catastrophic flooding.

Other chemical plants have also shuttered production in Texas because of the hurricane.

(Reporting by David Shepardson in Washington; Editing by Sandra Maler and David Gregorio)